1. Field of the Invention
The present invention relates, in general, to steering columns for motor vehicles.
2. State of the Art
Conventional steering column apparatus or assemblies for motor vehicles include an elongated, axial steering column shaft which is connected at one end to a steering wheel and at a lower end to a tail shaft. A jacket concentrically surrounds at least a portion of the steering column shaft, with the ends of the steering column shaft extending outward from opposed ends of the jacket.
Various brackets are mounted on the jacket to mount the jacket in the vehicle and to attach various devices, such as an ignition lock, steering column switch modules and control levers, etc., to the jacket. For tiltable steering columns, a bracket containing a pivot and a release lock lever mechanism is also mounted on the jacket, typically intermediate the ends of the jacket to provide selective tilting of the steering column apparatus to accommodate a driver's size and driving position preference.
Since the steering column jacket is made of metal, i.e., steel, the brackets are typically attached to the jacket via welding. However, this creates several disadvantages. The brackets mounted on the jacket are also made of metal which adds significant weight to the steering column apparatus. Welding operations are also costly in terms of labor and/or welding equipment. Welding also has uncertain reliability since there is no convenient way to determine if a proper high strength weld has been made, without resorting to destructive testing. Misaligned brackets or brackets attached to the jacket with low strength welds result in scrap which adds to overall costs.
The construction of the steering column shaft in a conventional steering column apparatus encounters similar problems. Typically, the steering column shaft is a solid, metallic tubular member. The lower yoke and upper threaded member separate members which are welded to the shaft to connect the steering column shaft to the lower tail shaft and the steering wheel, respectively. This entails the use of additional, separate elements which results in a higher overall weight for the steering column shaft, higher cost due the use of additional components and potential reliability problems when the yoke and threaded member are welded to the tubular shaft.
Thus, it would be desirable to provide a steering column apparatus which is constructed without any welds. It would also be desirable to provide a steering column apparatus in which the various mounting, tilt and accessory brackets are attached to the steering column jacket without the use of welding operations. It would also be desirable to provide a steering column apparatus which includes a steering column shaft which is constructed without the use of welding. It would also be desirable to provide a steering column shaft which is constructed as a one-piece, integral member without the use of separate members welded to a tubular shaft as is conventional. Finally, it would be desirable to provide a steering column apparatus which has a lower manufacturing cost, lower weight, greater manufacturing adjustability and greater reliability than conventionally constructed steering column apparatus.